Rusted

Thanks Pete.

I can hardly believe I managed to extract a single image from the recent seeing conditions. Wall to wall sunshine and it keeps defocusing. Image too soft to focus in [less than] SharpCap. Thermal wobbles all over the place! There's supposed to be a light bridge on AR2960! Stop laughing at the back!

Hi Nigella, I tried to warn you about overdosing Astrocat on ImPPG. Don't even get me started on black cats and thermal issues with solar imaging! A tabby is your best bet pet for both day and night imaging. Best of both worlds!

I think a more accurate term would be "polar altitude adjuster." [Or PA thumb screw] But then I'm a pedant. Not to be confused with peasant. Which is also true.

Ideally an equatorially mounted telescope is balanced around a point at the crossing of the mounting axes. If it were not balanced, then the nose, or tail of the scope, would rise or fall. It shouldn't do either. If it were not balanced then the counterweights, or the OTA, would rise or fall. Again it shouldn't do either. This image shows the crossing of the axes. Polar [RA] and Declination. The vertical line represent a perpendicular dropped from the crossing of the axes. The horizontal line shows the offset [or distance] of this perpendicular line from the tripod head. This offset represents a turning force trying to tip the tripod over. It also applies an increased force against the altitude adjustment screw.

Some of our local DIY, big shed stores sell assorted thumb wheels and knobs. Take along your original thumb screw to ensure the threads match. Balance is just as important to an altaz as it is to an equatorial. That's an awful lot of stuff perched [un]balanced high on top of a very little mounting. IMO. Worse, the mass is offset relative to the very narrow base. With all mountings it is the smallest cross section which matters under load. Your whole system is a compound pendulum. Look it up. I'm sorry, but I really wouldn't start from here if you want steady support. Which is exactly what that altitude screw is trying to tell you. In case of doubt: I have been overloading telescope mountings for over 60 years.

Barry rang me in the middle of dinner to repeat the nonsense he said back then. My dinner was getting cold. So I hung up. EDIT: I recorded the wheel numbers on my blog. 567 & 568. Making them consecutive.

An excellent set of images!

I have both a Lacerta 2" wedge and a Lunt 1.25". Both give excellent views and are also used for imaging. The Brewster angle can be a problem for visual use in tight spaces. I can't get my head behind the Lacerta wedge at certain solar altitudes. Because my dome base ring gets in the way. Others won't suffer from this problem. A solar foil filter protects the telescope's innards. While a wedge allows the full, focused heat of the sun to pass right through the telescope. This requires much greater care at the eyepiece end to avoid injury or even fire. For example: A plastic, focuser dust plug will readily burn if you have removed the wedge for safe storage. As I did only recently. When I safeguarded the instruments due to a dangerous storm warning. It is safer to have a cap for the dewshield until you are certain you have the wedge properly fitted. A secure, opaque cap for the finder too! The rotating polarizing filter is a great wedge accessory. Well worthwhile to set comfortable viewing brightness. Just remember to minimize the light cut if you decide to image. Or your exposures could get very, very long!

I have been looking back though my blog and corrected the delivery date of the Beacon Hill worm wheels to August 2016. https://fullerscopes.blogspot.com/2016/08/2-shaft-mouting-pt24-wormwheels-arrive.html Once the worms and wheels were actually fitted to the mounting they produced a very loud, "graunching" noise on driven slews. This was due to the extreme roughness of the machined surfaces of both worms and wheels. This was after I had scrubbed the teeth with a fine wire brush and paraffin. I had no plans to embed the obvious grit in the "precision" machined surfaces. The toothbrush had zero impact on the embedded filth in the teeth! It was completely impossible to run the worms against the worm wheels dry. [Without lubrication] There was far too much friction! Having been told by Barry Watts not to use anything but oil to "lap them in" I resorted to hours of free running the RA worm against the worm wheel driven by an en electric drill. I tried an assortment of fine abrasives [like Brasso which sprayed everywhere.] All without much improvement in the hideous and loud "graunching" noise of the rubbing surfaces. Not only were the worms rough but they could be heard to change their racket with every revolution. So the brass worms [NOT stainless steel] were actually eccentric. The worms are glued onto the miserably short, steel shafts. Solvol Autosol is a polishing paste for chrome. It has a fine abrasive quality and stayed in place during the polishing operation. This finally helped after countless hours of "lapping." I am normally a polite person. At the time I was so ashamed at having been sent these inferior products that I went into full denial mode. I deliberately hid the tooth defects in all my blog images. I did not show the filthy, black teeth on arrival. Nor did I mention my endless mechanical problems on my blog. Which was a complete disservice if anybody followed my lead and bought worm and wheel sets from Beacon Hill. And as still recommended by NON GOTO AWR[Tech] UK. The vendor of an expensive and noisy stepper motor Goto, drive system. Which has never found a single object in all the time I have been using it. Not the sun, the moon nor any other object. Not once in ~5.5 years! Barry Watts of Beacon Hill Telescopes is the master of transparent excuses. No doubt a skill polished over lifetime of failing to supply on time. His [quote] "agricultural" mounts are the stuff of legend. For failing to arrive as promised and being more of a "project in progress" when they finally do get delivered. He failed to get me to accept 1" shaft holes on smaller wheels after a month of waiting. I had ordered 50mm in 14" and 11". It took another month to source the junk I was sent. No doubt out of his octogenarian machinist's scrap bin. With 60mm bores not the 50mm I had ordered. Which is what he finally sent me. His failure to clean the filthy worm wheel teeth is ample proof of his completely casual attitude to his paying customers. He had wrapped the circumferences in protective pipe insulation. Was this just another ploy to hide the hideous filth/truth? His flowery descriptions of his "products" are the stuff of complete and utter fantasy. These same descriptions clearly break UK consumer laws and have remained unchanged for years on his website. He maintains this as a sales and advertising website but denies being "online." "The finest worm wheel sets available in the UK." Not by a light year!

Thanks, but it looks like a poster painted with a coarse brush to my eyes. I tried stopping down to 100mm [from 150mm] but it didn't make any obvious difference. It must be the seeing conditions. At 55N the sun is still struggling for altitude.

Thanks for your encouragement. I see a strange sharpening or graining effect after processing. Here's my last image of the day. 16.08 [CET] Posted full size. Does anyone else see a vertical texture overlying the image?

I was wasting my time all morning with strangely grainy images. After lunch the first image was fine. Then it all went bad again.

I moved the overlapping tooth area away from the worm. Probably pointless, but I can never look beyond E-S-W due to trees.

The BH bearings were self-adjusting. Meaning that the bearings literally fell out of the holes in the flimsy channel on the fist slew. They were only held in with Shellac and the tiny grub screw!! With no active worms the telescopes were completely free to swing about the dome completely unrestrained! Any attempt to tighten the tiny grub screw literally locked up the bearing against all further rotation: Later I beefed up the Beacon Hill housings and fitted angular contact bearings. The stepper motors are in close fitting, square tubular sections for stiffness. Heavy gauge, aluminium angle now surrounds the BH worm housing channel. Note the four screws, per bearing, to retain the bearings in the BH housings. The washers just nip the outer races to prevent unwanted, linear motion. Or backlash!

1) That is a Beacon Hill worm wheel not a worm. 2) It has not "been in the wars." It has been badly hobbed on the wrong diameter blank. And/or without previous gashing with a slit saw and precision dividing head. 2) After months of delay and endless excuses Barry still could not supply the wheels I wanted with 50mm bores. Quote: "The 97 year-old craftsman, who worked in a tin shed, out on the moors, without heating, had finally decided to give up." No more making "the finest worm wheels available to man," for him. 3) Out of desperation I finally accepted 60mm bores and turned my own brass sleeves to compensate. I did so without removing them from the chuck and took only light cuts. Thereby hoping to minimize eccentricity. 4) I had to clean the teeth of the supplied worm wheels with a toothbrush and paraffin because they had been sitting for years in a filthy atmosphere. Most likely because the maker was far too ashamed to release them onto some poor unsuspecting sod who still had to pay full price. It was also highly fortunate {for Barry] that I was "abroad" and thus much less likely to return them for replacement due to the postage costs. Besides, Barry had already failed to provide the goods in the first place. What chance had I in reality of ever seeing the goods as ordered. I wanted a 14" RA wheel but had to make do with an 11". Which itself was not even to spec but undersized. 5) My worms were brass, mounted on steel shafts. Which were far too short to allow a standard timing pulley to safely grip outside the bearings. There were no "adjustable" sealed roller bearings. Just the bog standard deep groove cheapest bearings on the market with metal seals. "All housed" in the pathetically flimsy, short off-cuts of standard, channel profile alloy merely pretending to be worm housings. These "worm housings" can be seen to flex visibly when the telescope is manually rocked at the eyepiece. The metal outside the bearings is only a few mm thick on three sides! Quote from the virtual, ancient papyrus: Bragging about Beacon Hill's amazing drives on their sales website: It hasn't changed in living memory! To follow the movement of a celestial body with any degree of accuracy a worm and wheel set is essential. Ours are made from machining quality aluminium alloy and have accurately cut teeth precisely concentric to the bore of the wheel. The central boss is fitted with a nylon pressure pad which enables you to slew the telescope to a new position in the sky without disconnecting the motor drive. The matching stainless steel worms are held in sealed roller bearings in substantial brackets and are fully adjustable to eliminate any developing end float. They can be hand operated or supplied with a small synchronous motor powered from the mains or through a 12V converter unit. They are the most accurate worm and wheel sets available to astronomers in this country. Sales of Goods Act? Not of merchantable quality? Fraudulent, false advertising? Trading standards Office? Where should we start?

It's good to see British engineering precision is still in safe hands! Supplied by Beacon Hill in [EDIT] August of 2016.

My posts are not appearing after I "submit." It just says "saving" but the post does not shown as published.

Be aware that long refractors are very demanding of the telescope mounting. They also require very tall and stiff piers [or tripods] to be able to "get under" the eyepiece. Even with a star diagonal or solar wedge in place you can easily find you develop permanently muddy knees.

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There is also the matter of having live "mains" electricity associated with the mounting in a [normally] damp environment. https://fullerscopes.blogspot.com/2011/10/fullerscopes-drives.html?m=0 These days, telescope mountings tend to use much lower voltages and stepper motors, for vastly more sophisticated control of drive speeds.

It is called a Hargreaves strut. It moves with the telescope tube and and declination axis. Reinforcing the tube and declination axis against possible flexure by simple triangulation. Large refractors have very heavy lenses [and cells] with considerable moment. [Moment = mass x distance from a pivot point]

All me own work guv: My 7" f/12 and 6" f/10. Mounted on my home made GEM built from scrap aluminium plate. Galvanized steel, dust extractor ducting for the telescope tubes. 50mm stainless steel shafts in flange bearings. Multi-axis compression studding for stiffness. Combination of shafts and disks for increased steadiness. All housed in my entirely home made 3m/10' plywood dome on top of my entirely home made, two story observatory with 14' pier. 7" f/12, in folded form, on my home made mounting with temporary, top RA drive. When I were a lad: 5" f/15 and 12" f/5 entirely home made including the optics. Mid 1980s. The observatory in winter. Presently being enlarged for a 4.2m/ 14' Ø GRP dome.

If you use the 135mm D-ERF on a 159mm it will reduce the aperture. You could insert the D-ERF inside the 159mm but it is not an easy task. It will almost certainly interfere with the telescope's baffles. Requiring their removal or being moved further away. Making them pointless. The 159mm objective could be removed to allow easier access for this work. The reflected energy from the face of the D-ERF will exit the objective in a fiercely hot, focused beam. The objective effectively doubles up on refocusing the original f/5.6 to a much shorter beam without ANY loss of solar energy! The D-ERF reflects 99% of the sun's heat without ANY filtration. The danger is extreme for anyone looking closely into the dewshield unless they manage to block all the sunlight with their head. I set fire to a temporary cardboard aperture stop in the dewshield before I realized the very real danger from the reflected beam.